Method to sustain minimum required aspect ratios of diamond grinding blades throughout service lifetime

ABSTRACT

Embodiments of the present invention generally relate to a blade for isolating devices within a wafer and the method of isolating. The blade has a core material, a cutting material disposed on the core material, and a plating material covering a portion of the core and cutting materials. The edge of the blade is not covered by the plating material. During operation, a portion of the plating material is removed to expose the underlying core and cutting materials based on the wearing of the core and cutting materials at the edge of the blade.

BACKGROUND

1. Field

Embodiments of the present invention generally relate to semiconductor device fabrication, and more particularly, to a blade for dicing substrates.

2. Description of the Related Art

Die separation, or dicing, by sawing is the process of cutting a thin film microelectronic substrate into individual devices, such as sliders containing read/write recording devices, with a rotating abrasive saw blade. Dicing by sawing provides versatility in selection of depth and width (kerf) of cut, as well as selection of surface finish, and can be used to saw either partially or completely through a substrate or wafer. Wafer dicing technology has progressed rapidly, and dicing is now commonly used in most front-end thin film packaging operations. Dicing is used extensively for separation of die on thin film integrated circuit wafers.

A wafer's device density is ever increasing to reduce unit costs. As a result of device density increase within a wafer, the channels between devices are continually decreasing. This decreasing in spacing demands that saw blade thickness be reduced. Blades are typically installed into hubs/arbors which support the blade with precision flatness and concentricity. The protrusion of the blade from the support of the hub is used to perform the cutting. The unsupported portion of the blade exposed for cutting dictates the aspect ratio of the blade, which equals to unsupported blade exposure divided by blade thickness. With the constant blade exposure, as the blade thickness decreases, the aspect ratio increases. The larger the aspect ratio of a blade is, the more the stiffness and cutting control degrade. Cutting with a high aspect ratio blade results in reduced cutting performance due to the lower effective blade stiffness and increased vibration.

Therefore, an improved blade is needed.

SUMMARY OF THE INVENTION

Embodiments of the present invention generally relate to a blade for isolating devices within a wafer and the method of isolating. The blade has a core material, a cutting material disposed on the core material, and a plating material covering a portion of the core and cutting materials. The edge of the blade is not covered by the plating material. During operation, a portion of the plating material is removed to expose the underlying core and cutting materials based on the wearing of the core and cutting materials at the edge of the blade.

In one embodiment, a blade for isolating devices is disclosed. The blade comprises a core material having a center and a first diameter, a cutting material disposed on the core material, and a plating material disposed on a portion of the core material and the cutting material. The plating material shares a same center with the core material and has a second diameter that is less than the first diameter.

In another embodiment, a blade assembly for isolating devices is disclosed. The blade assembly comprises a spindle hub and a blade coupled to the spindle hub. The blade comprises a core material having a center and a first diameter, a cutting material disposed on the core material, and a plating material disposed on a portion of the core material and the cutting material. The plating material shares a same center with the core material and has a second diameter that is less than the first diameter.

In another embodiment, a method for making a blade is disclosed. The method comprises depositing a cutting material on two sides of a core material, and depositing a plating material on the two sides of the core material. The plating material covers the core and the cutting materials. The method further comprises removing a portion of the plating material to expose underlying cutting and core materials.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 is a plan view of a blade according to one embodiment of the invention.

FIG. 2 is an exploded view of the blade according to one embodiment of the invention.

FIG. 3 is a cross sectional view of a blade assembly according to one embodiment of the invention.

FIG. 4 illustrates a processing sequence of making the blade according to one embodiment of the invention.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.

DETAILED DESCRIPTION

In the following, reference is made to embodiments of the invention. However, it should be understood that the invention is not limited to specific described embodiments. Instead, any combination of the following features and elements, whether related to different embodiments or not, is contemplated to implement and practice the invention. Furthermore, although embodiments of the invention may achieve advantages over other possible solutions and/or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the invention. Thus, the following aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to “the invention” shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s).

Embodiments of the present invention generally relate to a blade for isolating devices within a wafer and the method of isolating. The blade has a core material, a cutting material disposed on the core material, and a plating material covering a portion of the core and cutting materials. The edge of the blade is not covered by the plating material. During operation, a portion of the plating material is removed to expose the underlying core and cutting materials based on the wearing of the core and cutting materials at the edge of the blade.

FIG. 1 is a plan view of a blade 100 according to one embodiment of the invention. As shown in FIG. 1, the blade 100 includes a core material 102, a cutting material 104 and a plating material 108. A hole 110 is disposed in the center of the core material 102 and the plating material 108. The core material 102 may be a metal such as steel or nickel, or may be a composite material, and the cutting material 104 may be particles of hard crystals such as diamond or cerium oxide. The cutting material 104 is bonded to the core material 102 by any suitable bonding method, such as metal bonding or resin bonding. The plating material 108 may be a material that wears at a slower rate than the core material 102 having the cutting material 104 bonded thereon. In one embodiment, the plating material 108 is the same material as the core material 102. Once plated, the core material 102 may wear much slower than the plating material 108 even if materials are the same because the cutting material 104 is a reinforcing phase in the metal matrix of the blade. In one embodiment, both the core and plating materials are a metal such as nickel. The plating material 108 does not cover the entire core material 102 and cutting material 104. The edge of the blade 100 is not covered by the plating material 108, thus the core material 102 and the cutting material 104 at the edge of the blade 100 are exposed. This exposed portion of the core material 102 and the cutting material 104 is the cutting portion 112. The hole 110 is for securing the blade 100 to a blade assembly. The blade 100, the core material 102 and the plating material 108 as shown in FIG. 1 are all circular, but the shape is not limited to circular.

FIG. 2 is an exploded view of the blade 100 according to one embodiment of the invention. The cutting material 104 may be disposed on a portion 202 of the core material 102. The portion 202 extends from the edge of the core material 102 to an inner circle 204. The cutting material 104 is not disposed in the area within the inner circle 204. The size of the inner circle 204 depends on the securing device of a blade assembly. When the blade 100 is placed in a blade assembly, the securing device covers the area within the inner circle 204, thus the cutting material 104 is not covered by the securing device. The plating material 108 may have the same center as the core material 102, which is the hole 110. The plating material 108 may have a smaller diameter than the core material 102, thus the edge of the core material 102 having the cutting material 104 disposed thereon is not covered by the plating material 108.

As the device density increases within a wafer, the channels between devices are getting smaller which leads to thinner cutting portion of saw blades. As the cutting portion 112 gets thinner, the blade aspect ratio increases if the blade exposure, indicated as “D” in FIG. 1, remains constant. Beyond an aspect ratio of 30, significant degradation in performance such as increased chips and cracks, increased skew and reduced mean targeting may be observed. The blade exposure may have a minimum length due to several factors such as thickness of the wafer, minimum clearance between the wafer and the blade, and minimum undercut. In addition, the blade exposure may be reduced during operation as a result of wearing of the cutting portion 112. Thus, a blade having the minimum blade exposure may be changed out often, leading to an increase in cost.

To maintain a low aspect ratio while increase the service time of the blade, the plating material 108 is deposited on both sides of the core material 102 covering a portion of both the core material 102 and the cutting material 104. The plating material 108 may be much thicker than the core material 102, thus providing support and desired stiffness. Conventional blade support such as spacers may not be needed as a result. During operation, a portion of the plating material 108 may be removed to expose the underlying core material 102 and cutting material 104 as the blade exposure decreases due to wearing. The portion of the plating material 108 may be removed as a result of contacting the material that is being cut, or may be removed by a dressing stick, such as an aluminum oxide stick. The wearable plating material 108 provides support for the thin cutting portion 112 and provides a way to control the blade exposure. The blade exposure may be maintained at a minimum length, leading to a low aspect ratio.

In one embodiment, the thickness (into the paper) of the cutting portion 112 is about 50 to 70 micrometers (μm) and the thickness (into the paper) of the plating material 108 is over 200 μm, so the thickness of the blade 100 at an area with the plating material 108 is over 250 μm. In one embodiment, the blade exposure is about 1.25 mm and the thickness of the cutting portion 112 is about 50 μm, which leads to an aspect ratio of 25. In another embodiment, the blade exposure is about 1.25 mm and the thickness of the cutting portion is about 70 μm, which leads to an aspect ratio of 17.9. Both embodiments provide a blade having an aspect ratio of less than 30.

FIG. 3 is a cross sectional view of a blade assembly 300 incorporating the blade 100 according to one embodiment of the invention. The blade 100 is secured to the blade assembly 300 by a spindle hub 302. The blade 100 has the cutting portion 112 including the core material 102 and the cutting material 104 (not shown) and the plating material 108.

FIG. 4 illustrates a processing sequence 400 for making the blade 100 according to one embodiment of the invention. The processing sequence 400 starts with step 402, which is depositing a cutting material on a core material. The core material may be a circular disk and the cutting material is deposited on both sides of the core material. The core material may be a metal such as steel or nickel, or may be a composite material, and the cutting material may be particles of hard crystals such as diamond or cerium oxide. The cutting material is bonded to the core material by any suitable bonding method, such as metal bonding or resin bonding. The thickness of the core material is based on the width of the channels between devices located on a wafer. In one embodiment, the core material may have a thickness of about 50-70 μm.

Next, at step 404, a plating material is deposited on the core and cutting materials. The plating material covers both sides of the core material and the cutting material deposited on the core material. The plating material may be a material that has good adhesion to the core material and has a slower wearing rate compared to the base material reinforced by the cutting material. In one embodiment, the plating material is the same as the base material. The plating material on both sides of the core material may have a combined thickness that is much greater than the thickness of the core material. The thick plating material provides support and desired stiffness, thus, conventional blade support such as spacers are not needed. In one embodiment, the plating material on both sides of the core material has a combined thickness of over 200 μm.

Next, at step 406, a portion of the plating material at the edge of the blade is removed to expose the underlying core and cutting materials. The removal process may be achieved by any conventional removing process, such as dressing by an aluminum oxide stick. During operation, a portion of the plating material may be further removed to expose the underlying core and cutting materials, as the core and cutting materials at the edge are worn off. The removal of the portion of the plating material during operation may be achieved by dressing or by contacting the plating material with the material being cut. The portion of the plating material may be removed after a single cut or after multiple cuts.

In summary, a blade having a plating material covering a portion of the core and cutting materials is disclosed. The thick plating material provides support for the blade and provides desired mechanical stiffness. The wearable plating material provides a way to maintain a low aspect ratio while increase the service time of the blade.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

What is claimed is:
 1. A blade for isolating devices, comprising: a core material including a center and a first diameter; a cutting material disposed on the core material; and a plating material disposed on a portion of the core material and the cutting material, wherein the plating material shares a same center with the core material and has a second diameter that is less than the first diameter.
 2. The blade of claim 1, wherein the core material is formed of a metal.
 3. The blade of claim 2, wherein the cutting material is formed of diamond particles.
 4. The blade of claim 3, wherein the plating material is formed of a same material as the core material.
 5. The blade of claim 1, wherein a difference between the first diameter and the second diameter is about 1.25 mm.
 6. The blade of claim 5, wherein the core material has a thickness of about 70 μm.
 7. The blade of claim 6, wherein the plating material has a thickness of about 200 μm.
 8. The blade of claim 5, wherein the core material has a thickness of about 50 μm.
 9. A blade assembly for isolating devices, comprising: a spindle hub; and a blade coupled to the spindle hub, wherein the blade including: a core material having a center and a first diameter; a cutting material disposed on the core material; and a plating material disposed on a portion of the core material and the cutting material, wherein the plating material shares a same center and a second diameter that is less than the first diameter.
 10. The blade assembly of claim 9, wherein the core material is formed of a metal.
 11. The blade assembly of claim 10, wherein the cutting material is formed of diamond particles.
 12. The blade assembly of claim 11, wherein the plating material is formed of nickel.
 13. The blade assembly of claim 9, wherein a difference between the first diameter and the second diameter is about 1.25 mm.
 14. The blade assembly of claim 13, wherein the core material has a thickness of about 70 μm.
 15. The blade assembly of claim 14, wherein the plating material has a thickness of about 200 μm.
 16. The blade assembly of claim 13, wherein the core material has a thickness of about 50 μm.
 17. A method for making a blade, comprising: depositing a cutting material on two sides of a core material; depositing a plating material on the two sides of the core material, wherein the plating material covers the core and the cutting materials; and removing a portion of the plating material to expose underlying cutting and core materials.
 18. The method of claim 17, wherein the plating material is formed of a same material as the core material.
 19. The method of claim 18, wherein the removal of the portion of the plating material is performed with a dressing stick.
 20. The method of claim 19, wherein the dressing stick is formed of aluminum oxide. 